feat!: Merge ‘stack’ and ‘inside’ space categories and update components

[VincentSmedinga]

This merges the ‘Stack Space’ and ‘Inside Space’ categories to just ‘Space’.

The medium space widths are equal to the font sizes of Text Level 5: in Spacious Mode, it grows from 18px at 320px wide to 24px at 1600px wide. The smaller sizes are 50% and 25% of the medium width, the larger are 150% and 200%. So Spaces grows linearly, while Type grows exponentially. We’ll have to see if this doesn’t become weird, but it does make it simpler for now, especially in Figma, with only 2 lengths that aren’t integers.

I’ve made an inventory of all components using these types of space (paddings, gaps, and some margins) and applied them consistently. A next step can be to introduce some common spacing tokens, e.g. ams-text-input-appearance-padding-inline and ams-list-appearance-gap, which express some underlying design choices.